In a related optical signal transmission technology, a WDM (Wavelength Division Multiplex) system is utilized as a communication system in which a plurality of optical signals each having a different wavelength is multiplexed to one optical fiber cable. In an optical packet transmission system to which the WDM system is applied (hereinafter, described as a “WDM transmission system”), an optical packet transmission device temporarily converts a packet received from a client terminal via Ethernet (registered trademark) into an electrical signal, and then converts the electrical signal into an optical packet again to send out the converted optical packet to a WDM line as an optical transmission path. When sending out an optical packet, the optical packet transmission device divides the optical packet into a plurality of different wavelengths (for example, 10 wavelengths), and then multiplexes and transfers optical signals with the wavelengths. When an optical packet transmission device on a receiving side (hereinafter, described as an “optical packet receiving station”) receives the optical packet, the optical packet receiving station divides the optical packet into a plurality of different wavelengths and restructures the optical packet from optical signals with the wavelengths, and thereafter transfers the optical packet to a client terminal via Ethernet.
Patent Document 1: Japanese Laid-open Patent Publication No. 2000-151607
However, when an optical packet transmission device divides an optical packet into a plurality of wavelengths λ0 to λm-1 to be transferred, communication of the optical packet is cut off in some conditions. For example, when an E/O (Electrical to Optical) converter corresponding to wave length λ1, among the components of the optical packet transmission device on a transmission side (hereinafter, described as an “optical packet transmitting station”), suffers from a failure due to some factor, transmission in a portion corresponding to wavelength λ1, among the components of the optical packet in which the plurality of wavelengths is multiplexed, comes to be interrupted. However, the optical packet receiving station is unable to normally recover (restructure) the packet to be transferred to Ethernet, unless an optical packet with all wavelengths used in the transmission (for example, 10 wavelengths) is received. For this reason, there has been a concern that in the WDM transmission system in which an optical packet transmitting station divides an optical packet into a plurality of wavelengths to be sent out, communication at and after the optical packet receiving station becomes difficult to be continued when the above-described failure occurred.